Trick for function trace printing

[Dicebot via Digitalmars-d]

Noticing requests for addition of @trace attribute I decided to 
share one small snippet of mine:

=========
immutable trace =`
    import std.stdio : writefln;
    import std.string : format;
    import std.traits : ParameterIdentifierTuple;
    mixin(format(
        q{enum args = ParameterIdentifierTuple!(%s);},
        __FUNCTION__
    ));

    import std.algorithm : map, joiner;
    enum args_fmt = [args].map!(a => "%s").joiner(", ");

    mixin(format(
        q{writefln("> %s(%s)", %s);},
        __FUNCTION__,
        args_fmt,
        [args].joiner(", ")
    ));

    scope(exit)
    {
        mixin(format(
           q{writefln("< %s(%s)", %s);},
           __FUNCTION__,
           args_fmt,
           [args].joiner(", ")
        ));
    }
`;
=========

Used like this:

=========
module test;

void foo(int a)
{
    mixin(trace);

    bar(0.43, null);
}

int bar(double x, int* ptr)
{
    mixin(trace);

    return 444;
}

void main()
{
    foo(42);
}
=========

Prints

test.foo(42)
test.bar(0.43, null)
< test.bar(0.43, null)
< test.foo(42)

http://dpaste.dzfl.pl/3dd33973bc99

Is not optimized at all but gets job done for simple cases when I 
usually want it.

Hope it can be useful for someone else ;)